The present invention relates to smoking articles generally having a fuel element, a physically separate aerosol generating means, and a separate mouthend piece, and having improved means for delivering one or more volatile flavorants to the user which comprises a carbon filled sheet material located in a non-burning portion of the smoking article which bears or otherwise carries or contains one or more flavorants. As used herein, the term "smoking article" includes cigarettes, cigars, pipes, and other smoking products which generate an aerosol such as smoke. More specifically, the present invention is preferably directed to a carbon filled sheet, preferably containing tobacco, the sheet being employed as at least a portion of the mouthend piece of such articles to carry flavorants, particularly highly volatile flavorants like menthol.
Cigarettes, cigars and pipes are the most popular forms of smoking articles. Many smoking products and smoking articles have been proposed through the years as improvements upon, or as alternatives to, these popular forms of smoking articles, particularly cigarettes.
Many, for example, have proposed tobacco substitute smoking materials. See, e.g., U.S. Pat. No. 4,079,742 to Rainer et al. Two such materials, Cytrel and NSM, were introduced in Europe in the 1970's as partial tobacco replacements, but did not realize any long-term commercial success.
Many others have proposed smoking articles, especially cigarette smoking articles, based on the generation of an aerosol or a vapor. See, for example, the background art cited in U.S. Pat. No. 4,714,082 to Banerjee et al.
As far as the present inventors are aware, none of the foregoing smoking articles has ever realized any significant commercial success and none have ever been widely marketed. The absence of such smoking articles from the marketplace is believed to be due to a variety of reasons, including insufficient aerosol generation, both initially and over the life of the product, poor taste, off-taste due to thermal degradation of the smoke former and/or flavor agents, the presence of substantial pyrolysis products and sidestream smoke, and unsightly appearance.
Thus, despite decades of interest and effort, there is still no smoking article on the market which provides the benefits, advantages and pleasures associated with smoking, without delivering considerable quantities of incomplete combustion and pyrolysis products.
Recently, however, in European Patent Publication Nos. 0174645 and 0212234 and U.S. Pat. No. 4,714,082, assigned to R.J. Reynolds Tobacco Co., there are described smoking articles, especially cigarette smoking articles, which are capable of providing the benefits, advantages and pleasures associated with smoking, without burning tobacco or delivering appreciable quantities of incomplete combustion or pyrolysis products. The improved flavorant delivery means of the present invention are particularly suited for use with such articles.
Mentholated smoking articles represent a substantial portion of the total market. In fact, nearly one-third of all cigarettes produced are mentholated to some extent. However, one of the major problems with menthol and other volatile and semi-volatile flavorants applied to smoking articles is that the flavorants usually migrate to other components of the article. Such migration is well documented in the literature. See, e.g., Brozinski, M. et al., Beitrage zur Tabakforschug International 6, 124-130 (1972); Curran, J.G., Tobacco Science 16, 40-42 (1972); and Reihl, T.F. et al., Tobacco Science 17, 10-11 (1973).
In cigarettes, migration occurs whether the flavorants are incorporated into the tobacco, the filter, the wrapping materials, or on the packaging materials (e.g., mentholated foil). The end result for all such applications is similar. During storage, an equilibrium level of flavorant results, with the flavoring material migrating through the entire smoking article and associated packaging. The degree of migration depends on, among other things, the flavorant's vapor pressure, its solubility in the various components of the article, environmental conditions including temperature and relative humidity, the resistance to migration of the various materials (e.g., tobacco, wrapper, filter material, glue, etc.).
A number of attempts to solve migration-related problems have been made, but have met with limited success. For example, various chemicals have been employed such as chemically bonded non-volatile substances in order to reduce migration (e.g., beta-cyclodextrin menthol complexes, glucosides of menthol, menthol amides, esters, etc.). See, e.g., U.S. Pat. Nos. 3,426,011 to Parmerter et al. and 3,344,796 to Yamaji et al. In general, all of these compounds have limited application because of cost and because of the poor taste perceptions of the smoke delivered.
Others have studied the use of so-called microencapsulated flavorants in various locations in the smoking article. See, e.g., U.S. Pat. Nos. 3,550,598 and 3,540,456 to McGlumphy et al., Swiss Patent No. 475,418 to Baumgartner Papiers S.A. and Netherland Patent No. 8201585 to Dowve Egberts Koninklijke.
Still others have entrapped volatile flavorants into polymer systems such as linear low density polyethylene and inorganic filters e.g., CaCo.sub.3, aluminas, etc., and placed these materials in the form of pellets or strands or particles in the filter systems or packaging systems. The problems with this approach are that migration still occurs (albeit, in a controlled manner), the loads of flavorants required with such materials are often very high and cost prohibitive, and the overall delivery rates of flavorants are low, usually between 1-18% by weight based on applied levels.
The use of carbon in various components of cigarettes has also been proposed. Specifically, carbon has been employed in wrapper systems, as filler material, and in filter systems for the reduction of gas phase smoke constituents, as well as for the introduction of flavorants to the cigarette. See, e.g , U.S. Pat. Nos. 2,063,014 to Allen, 3,744,496 to McCarty et al., 3,902,504 to Owens et al., 4,505,202 to Cogbill et al., and 4,225,636 to Cline et al. However, carbon, and in particular activated carbon has not found significant commercial use as a carrier of flavorants such as menthol since, among other reasons, activated carbon adsorbs the greater part of menthol before it can be delivered to the smoker. In order to compensate for this phenomenon, the carbon material is generally saturated with flavorant. However, as noted above, this results in undesirable migration of the flavorant to other components of the smoking article. See, for example, U.S. Pat. No. 3,236,244 to Irby et al. which describes the use of activated carbon both to remove undesirable constituents from smoke as well as to introduce flavoring agents thereto.
U.S. Pat. No. 3,972,335 to Tigglebeck et al. acknowledged this problem. Tigglebeck discloses blocking the small pores of activated carbon with a pore-modifying agent such as sucrose. The pore-modifying agent is disclosed as being used in amounts such that the less retentive portions of the activated carbon are not blocked but remain available for adsorption of the flavorant. Purportedly, this increases the shelf life of the smoking article by reducing migration of the flavorant while allowing efficient release of the flavorant during smoking. However, there appears to be substantial migration in excess of about 40%. See Example I at columns 5-6. As a result, carbon filters or carbon wrappers have not generally been recommended for mentholated smoking articles.